Modern motor vehicles often include park assist systems. Park assist systems may encompass a variety of assistance functions. These include, for example,                a) distance warning (park distance control—PDC);        b) display of information about the suitability of a parking space, e.g., its dimensions;        c) driver assistance during parking, which may include the specification of a steering angle or even an automatic steering intervention; or        d) fully automatic parking.        
The assistance functions c) and d) usually require a steering intervention. This means that the steering of the motor vehicle must be actively modified during the course of the parking operation. This steering intervention may be implemented by the motor vehicle itself, in an automatically controlled manner. In the assistance functions c) and d), the motor vehicle calculates a setpoint path along which the motor vehicle is parked, or is to be parked, in the parking space.
A collision warning device for motor vehicles, which offers a functionality according to a), is described in German Published Patent Application No. 38 27 729. With the aid of the device described there, it is determined whether there is a risk of colliding with an obstacle on a course taken by the motor vehicle.
Described in German Published Patent Application No. 102 20 426 and German Published Patent Application No. 102 20 427 are park assist system which determine a size of a parking space, use it to calculate a potential parking sequence for the motor vehicle, and output instructions to a driver as to which direction the steering wheel has to be turned and in which manner the driver is to accelerate or brake the motor vehicle. Both documents also mention a specific arrangement in which the driver actuates the steering system and accelerates and brakes the motor vehicle independently. Furthermore, in each case a separate specific arrangement is described in which the vehicle is parked in or pulled out of a parking space in a fully automatic manner without a steering intervention and without an acceleration and/or a braking intervention. In addition, in German Published Patent Application No. 102 20 427 the advantageous sequence of pulling in and out of a parking space is visually displayed to the driver on a display device.
Furthermore, German Published Patent Application No. 103 54 661 describes a park assist system which is able to determine the size of a parking space, calculate a setpoint path, and provide a driver with information and instructions in connection with the parking operation, so that the driver can park the motor vehicle in the parking space along the specified setpoint path. The steering may be implemented automatically during a first, single-pass parking operation. In a different specific arrangement, it is provided that information about a steering direction and driving direction may be output for maneuvering.
PCT International Published Patent Application No. WO 2004/059408 describes a park assist system in which the parking space and the motor vehicle are shown to the driver together with a setpoint trajectory in a plan view of the parking situation. A slanted representation of the motor vehicle with respect to the parking space indicates that the driver can still align the vehicle in the parking space at the end of the parking maneuver in order to bring about an optimal parking position for the motor vehicle.
Park assist systems which park a motor vehicle in a fully automatic manner have a few inherent drawbacks. In fully automatic operations people tend to take their supervisory duties less seriously than they should. As a result, there is the risk that the driver of a motor vehicle equipped with a park assist system for fully automatic parking will neglect his duties of monitoring the parking space especially with regard to persons moving inside the area of the parking space. Furthermore, in particular for an inexperienced driver, it is not easy to predict which driving movements the motor vehicle will execute during parking. This makes it even more difficult to carry out the control duties. Assigning the control duties entirely to the motor vehicle requires very complex sensor systems that include redundancy and diversity, since movable objects, in particular, are difficult to detect by a motor vehicle. If a movable object, e.g., another moving motor vehicle, is not detected as a moving object, then the risk of a collision increases. It is for this reason that park assist systems which actively involve the driver in the parking operation so that he may tend to the supervisory duties but which still relieve him of a portion of the tasks during parking, are preferred these days.
The conventional semi-automatic park assist systems all have in common that they can render assistance in a one-pass parking operation leading to an optimally aligned parked motor vehicle only if the parking space is of sufficient size, specifically of sufficient length. However, in particular in cities where motor vehicles are frequently parked along the side of the road parallel with the road's extension, parking spaces are rarely marked. The parking space dimensions thus vary considerably. However, parking spaces of sufficient size in which the motor vehicle may be parked in a single pass with the aid of a park assist system according to conventional arrangements are often difficult to find for a driver. The motor vehicle may thus indeed be parked in the parking space at the end of a single-pass parking step, yet the orientation of the motor vehicle may deviate from a setpoint orientation, which usually is in parallel alignment with a longitudinal edge of the parking space. A single pass operation denotes a parking step in which the motor vehicle is moving continuously and no change in a turn direction of the motor vehicle takes place.
PCT International Published Patent Application No. WO 2004/059408 describes a park assist system in which a subsequent maneuvering direction is indicated to the driver by an arrow. However, the problem of modifying the alignment of a motor vehicle with regard to its orientation in a parking space with the aid of a semi-automatic park assist system is not solved in an altogether optimal manner. The same problem of modifying the alignment of the motor vehicle also arises when the motor vehicle is to be pulled out of the parking space. The goal of a pullout parking operation is to modify the motor vehicle's orientation such that the motor vehicle is subsequently able to be moved out of the parking space in a single pass.